Iron pit props



W. ZINDEL IRON PIT PROPS May 15, 1956 2 Sheets-Sheet 1 Filed Feb. 12, 1953 llVVE/VUP WILLI ZINDEL Li B! Wu. W

Attorney W. ZINDEL IRON PIT PROPS May 15, 1956 2 Sheets-Sheet 2 Filed Feb. 12, 1953 FIG. 7

lA/VEA/TGP WILLI ZINDEL Attorney Unit-6d il Pa ent o i IRON PIT PROPS Willi Zindel, Bochum, Germany Application February 12, 1953, Serial No. 336,603

Claims priority, application Germany February 26, 1952 7 Claims. (Cl. 248-354) The invention relates to collapsible metal pit props of the kind comprising an upper and a lower portion -which are connected with one another by a clamping lock, and the object of the invention is to provide a pit prop of this kind-which is distinguished from the known constructions in that it is of particularly simple design, and easy to operate; that is it can be fitted and dismantled easily, independent or' the thickness of the seam, and the transmission ratio of the friction faces in the lock, which determines its collapsing characteristic, can be easily selected at will, viz. very high, to 1:4 and more.

These advantages are attained according to the invention in that contrary to the known constructions, in which the clamping lock is fixedly connected to the lower portion of the prop and forms an integral part of it, the clamping lock forms a separate component which accordingly is rigidly connected neither to the upper portion nor to the lower portion of the prop and on which the upper portion acts directly.

A further basic difference from all known prop constructions consists in that the lower portion of the prop comprises a profile having a cruciform cross section, and the upper portion consists of a tubular profile, into which the cruciform profile of the lower portion is telescoped in the course of the collapsing of the pit prop when taking pressure.

The lock is so constructed that the recesses of the cruciform profile are engaged by a corresponding number of friction bodies, which are pressed by a sleeve enveloping the same on to the profile of the lower portion of the prop at a pressure capable of being appropriately selected.

By constructing the friction bodies, which are conveniently made of angular cross section, wedge-shaped at the front edge of the flanges, the sleeve enveloping the friction bodies is further tensioned beyond the initial tension by the action of the pressure of the upper portion of the prop acting on the same, and thereby the friction on the lower portion of the prop is increased.

In order to tension the sleeve, means known per so can be used. It is preferable, from the point of view of safety and ease of operation, to construct the sleeve in the manner of a clamping sleeve the turned up lugs of which are surrounded by a clamping sleeve, which is tightened by wedge means and which can be loosened by removal of the said wedge means.

it is obvious that the construction of the pit prop according to the invention as described in principle herein is not comparable to known constructions in which an upper portion of the prop, having a cruciform profile, is clamped against a tubular lower portion of the prop by means of a lock which is fixedly connected to the said lower portion.

Further features and details of the invention will be apparent from the following description with reference to the accompanying drawings, in which preferred embodiments of collapsible props according to the invention are illustrated.

v 2,745,622 Patented May 15, .1956

Figure l is a longitudinal section of one embodiment of prop; I

Figure'2 is a similar view of another embodiment in longitudinal section, and

Figure 3 is a side elevation offset relative to Figures land 2; v

Figure 4 is a horizontal section through the lock;

Figure 5 shows an embodiment of the tensioning device for the band or strap;

Figures 6 and 7 are a frontal and a side elevation, respectively, on a larger scale, of another embodiment of the lock;

Figures 8 and 9 are a section and a part-section, respectively, of two different embodiments of the tensioning device.

The pit prop according to the invention comprises alower portion 10 of cruciform section, a tubular upper portion 11, anda lock, which is independent ofboth of them, and which comprises essentially a wedge piece 12 contacting the flanges of the lower portion of the prop, and of a frusto-conical sleeve 13 holding the same together. base plate 14, and the upper portion 11 of the prop has the usual head 15. The upper portion 11 has moreover the usual rows of slots 16 for setting the prop to the length desired by means of the setting wedges 1 7., Bysuitable means, such as transverse pins, dowels or the like, 18, the lock formed by the sleeve 13 and the wedges 12 is held on the upper end of the lower portion of the prop. The Wedge bodies 12 have at their uPPer ends noses .19 by means of which they rest in the initial position on the upper edge of the sleeve 13. Atthe lower ends of the wedge bodies 12 liekwise noses 20 are provided, on which the sleeve abuts when it slides along the front edges 21 of the wedge bodies 12. The difference between the friction face on the sleeve and the friction face on the wedge bodies 12 on the flanges of the lower portion 10 of the prop determines the degree at which the band or strap is carried along by the upper portion 11 of the prop resting on the upper edge of the sleeve 13. The sleeve13 is in the form of a truncated conical clamping ring, and is combined with a tensioning device 23, which is arranged on or above the turned up lugs 22. The tensioning device may consist according to Figures 5 to 7 of a sleeve 24 pushed over the lugs 22. This sleeve may be tightened by being shifted over the lugs 22 in one direction and loosened by being shifted in the other direction, the sleeve acting as an abutment.

In the embodiment according to Figure 5 moreover a wedge body 25 extends between the lugs 22 and the sleeve 13, which body, when tightening the device clears the space between the lugs 22, and drives the same apart when loosening the device.

By forcing the wedge 26a to the left of Figure 5, it will be understood that the wedge body 25 is forced upwardly by the sleeve 24 between the lugs 22 thus loosening the assembly by causing the lugs to be spread apart. On the other hand, by driving the wedge 26 inwardly or toward the right of Figure 5, the sleeve 24 is forced downwardly and enabling downward movement of the wedge body 25 and causing movement of the lugs toward each other to an extent limited by the wedge 25. In effecting these adjustments, it is manifest that both of the wedges must be moved in opposite directions at substantially the same time, so that tightening or loosening of the sleeve 13 on the lower prop portion may be achieved. Both wedges are guided in cut-outs of the lugs 22 of the sleeve, and may be safeguarded against being lost by transverse pins 27, 27a. The lower edge 28 of the tightening sleeve 24 serves as an abutment for the wedge 26, and the upper edge as an abutment for the wedge 26a.

In the embodiment according to the Figures 6 and 7 the The lower portion 10 of the prop has the usual pair of tightening wedges is combined, and is passed through the middle of the lugs 22 of'the sleeve 13. The' tightening sleeve 24 is brought into the clamping or loosening position by the respective faces of the double wedge 30, 31 coming into contact, respectively similarly to what is done in Figure by the separate pairs of Wedges. The guide wedge 25a is in this embodiment inserted into the gap in the tightening sleeve 24 so as to fill the same. In this embodiment, the transverse pins 32 at the same time hold the two wedges and 31 together and limit their path. For example in this embodiment the wedge 39 abuts on the slot faces 33 of the tightening sleeve, and on the slotfaces 34 in the lugs 22 of the sleeve 13. The abutment of the wedge 31 is formed by the tightening sleeve 24 and by the lugs 22 of the sleeve 13 in the inverse form and sequence. The pair of wedges 30, 31 is so guided in the corresponding slots of the lugs 22 of the sleeve 13 that in the process of tightening the abutments of the counter-wedge, and

in .the process of loosening the inversely operating abutments, the tightening sleeve 24 and the central wedge 25a are released.

The setting of the pit prop is effected by pulling the upper portion 1.1 onto the upper edge of the clamping lock 13 etc. which loosely rests on the upper edge of the lower portion 10. The upper and lower portions of the prop are subsequently clamped in the usual way between the roof and the floor by the setting wedge 17 being driven successively into the row of slots 16. Then the clamping lock 13 etc. is pulled under the lower edge of the upper portion 11 and then the sleeve 13 is drawn firmly over the wedge body 12 by means of thetightening device, the noses 19 of the wedge bodies resting on the upper edge of the sleeve 13. When the upper portion of the prop begins to take up pressure, it is forced along the wedge faces 21 owing to the lesser wedge faces and consequently smaller friction, while the lock and accordingly the wedge bodies are further pressed against the lower portion of the prop, until the lower edge of the sleeve 13 has reached thenoses 20 of the wedge bodies 12. The diiference of the friction faces 21 as against the friction faces on the lower portion 10 of the prop determines the magnitude of the pressure taken up in the first phase, until the sliding oif and/or collapsing of the prop begins. The loosening and/or removal of the pit prop is effected by forcing-in the transverse wedge aggregates 26 or 30, the wedges 26a or 31, respectively moving in the opposite direction. In order to safeguard the function of the wedge bodies 12, it is convenient to select the angle included between the flanks of two flanges of the lower portion of the prop of the contact faces 39 not merely 12:90", but b=92 or more. With rolled cruciform profiles this angle results already from the necessary chamfer of the rollers.

Safeguarding of the action of the wedge bodies 12 can moreover be attained alternatively or additionally so that the front edges 21 of the angle wedges are not merely made easily slidable, but in that the friction coefiicient is improved by roller bodies. These roller bodies 36 may be inserted singly and abut on the sleeve.13, or they may be combined by rods 37 or the like and run in recesses 38 of' the front edges of the wedge bodies 12. The shape of the roller bodies 36 may be trunconical, cylindrical, belled or the like.

Obviously the invention is not limited to the embodiments described hereinabove in detail and illustrated in the drawings, but numerous modifications thereof are pos sible without departing from the scope of the invention.

I claim:

1. A collapsible pit prop comprising a tubular upper portion, a cruciform lower portion telescoping within the upper portion, a clamping lock connecting said portions, said lock consisting of a plurality of wedges tapering inwardly in a direction toward the upper prop portion; said wedges together forming a segmental frustoconical body, and a frusto-conical annular sleeve slidably fitting said segmental body, the lower edge of the upper prop portion resting directly upon the upper edge of said sleeve, thereby to exert pressure through the sleeve and wedges to the lower prop portion.

2. A pit prop according to claim 1 comprising relative- 1y straight up and down inner edge portions and tapering narrow outer edge portions; on the wedges the tapering portions contacting the clamping sleeve.

' 3. A pit prop according to claim 1 comprising abutment noses on each end of the clamping wedges for limiting the relative movement of the clamping wedges by engagement with the upper or lower edges of the clamping sleeve.

4. .A pit prop according to claim l in which the frusto-conical sleeve is split, later lugs on the ends of said split sleeve, a tensioning and loosening device comprising a tapered sleeve embracing said lugs, and two transversely positioned wedges adapted to be driven into said tapered sleeve for tightening the clamping lock.

5. A pit prop according to claim 4 comprising lateral lugs on the clamping sleeve, and a wedge guided between said lugs coacting with the loosening wedges of the clampin g sleeve.

6. A pit prop according to claim 1 comprising lateral lugs on the clamping sleeve, two tensioning and loosening wedges arranged side by side and disposed between said lugs, and pins connecting the ends of said wedges.

7. A pit prop according to claim 4, comprising rollers in the parts contacting the clamping sleeve thereby to reduce the friction transmittedbetween the edge of the clamping wedges contacting the clamping sleeve and the faces ofthe lower portion of the prop.

References Cited in the file of this patent UNITED STATES PATENTS 830,497 Childers Feb. 4, 1952 FOREIGN PATENTS 618,559 Germany Sept. ll, 1935 670,635 Great Britain Apr. 23, 1952 801,089 Germany Dec. 21, 1950 830,497 Germany Feb. 4, 1952 

